This application relates to devices for pulling on conductive material, and may be used for proof testing, forming or dent removal, to name a few.
Electromagnetic forming of conductive materials has long been used with a high amplitude fast rise pulse of current to form conductive parts with a repulsing action. U.S. Pat. No. 3,124,726 discloses such a pushing type of forming where a massive hollow copper cylinder with a slit is used as a secondary coil to concentrate a pulsed primary current to radially compress a conductive part located in the axis of the cylinder.
U.S. Pat. No. 3,196,649 discloses a device for electromagnetic metal-forming by magnetic tension. This patent places a spiral, pancake type coil between a part to be formed and a secondary coil.
In U.S. Pat. No. 3,998,081, an electromagnetic puller for a conductive material had a coil first energized with a high amplitude current to set up a repulsing electromagnetic field slow pulsed to prevent deforming the conductive material; which was followed by a lower amplitude pulsed current to collapse the first field and set up an electromagnetic flux which pulled the coil and the part to be formed together with a force sufficient to remove dents. That patent also disclosed several coils shaped to act as flux concentrators to direct the electromagnetic forces to the desired area to remove dents. In application No. 646,068 other coils were disclosed which were shaped to act as flux concentrators, and application No. 726,872 disclosed a portable head with a flux concentrator for pulling out dents. The information contained in those applications, particularly the information describing the production and application of electrical current in the electromatic working coil of a dent removal head is incorporated herein by reference.